It’s the most unreliable way to vote, a last resort in which half of the ballots are disqualified. Created by Congress a decade ago, the provisional ballot was intended as a final attempt to preserve the right to vote for someone whose eligibility is in doubt. Florida saw a surge in such ballots in 2012 even though turnout was nearly the same as four years ago. The reason: a much-maligned law approved by Gov. Rick Scott and the 2011 Legislature that, among other things, required people moving to a different county to vote provisionally if they didn’t change their address a month before Election Day.

As a result, provisional ballots jumped an average of 25 percent in counties reviewed by the Times/Herald, further taxing elections officials struggling with extra paperwork from a separate rise in absentee ballots.

“It’s like pouring sand into the gears of the machine,” said Ion Sancho, the Leon County supervisor of elections, who had a 56 percent spike in provisional ballots, driven mostly by incoming Florida State students.

Supporters say the county-to-county requirement was needed to combat fraud and prevent people from voting twice by casting ballots in two counties. But those supporters lacked evidence that it happened, and the 2012 election didn’t bolster their case.

Interviews with elections officials and a preliminary review of 2012 provisional ballot figures show that type of fraud is essentially nonexistent.